1. Field of the Invention
The present disclosure relates to a fine pitch chip package structure and a bump structure thereof.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
As display panel technology is improved to provide higher resolution and higher-quality images, the number of bond pads for driving pixels necessarily increases. Correspondingly, as such increasing numbers of bond pads are placed on driving chips of ever-diminishing size, the research in chip on glass package technology or chip on flex package technology for driving chips of liquid crystal modules has focused on fine pitch chip package technology.
Generally, in a liquid crystal module, driving chips are attached to the display panel using an adhesive material as a middle layer, wherein the adhesive material can be an anisotropic conductive adhesive or a non-conductive adhesive. However, when driving chips are bonded using a fine pitch technology and an anisotropic conductive adhesive as a middle layer, conductive particles may easily aggregate between bumps, resulting in abridging issue causing shortage of bond pads due to the pitch of the bumps being less than 10 micrometers. To solve the bridging issue, different technologies have been developed.
U.S. Patent Publication No. 2007/0,063,347 discloses a type of conductive particle. Each of the conductive particles is enclosed by an insulative layer, thereby electrically isolating the aggregate conductive particles from each other.
U.S. Patent Publication No. 2005/0,227,475 discloses a method using an electrophoresis technology to control the distribution of conductive particles on the bond pads of a chip.
U.S. Pat. No. 7,109,058 discloses a semiconductor device without bumps thereon and a method for fabricating the same. The method attaches conductive particles to bond pads using an ultrasonic welding technology.
Aside from the above issues, as the density of bond pads increases, the bumps for connecting the bond pads become correspondingly smaller. With smaller bumps, the number of trapped conductive particles is smaller, reducing the quality of the connection between the bumps and the bond pads.
In summary, the chip package technology faces a fine pitch chip package challenge, and therefore a new bond pad bonding structure and method that can overcome the above-mentioned issues are required.